JP2009191992A - Sealing device for hydraulic shock-absorber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealing device used as shaft-seal means for a piston rod of a hydraulic shock-absorber wherein maintenance of sealing properties of a main lip, and reduction in sliding resistance attributable to a reduction in valve-opening pressure for a check-lip are made compatible with reversion-inhibition for the check-lip in back-pressure time. <P>SOLUTION: The sealing device includes a main lip 102 which is slidably contacted closely with the periphery of the piston rod 4, and a check-lip 105 which is provided on the periphery of the main lip 102, and extended taperingly slantingly to the periphery so as to be axially opposed to the valve-seat face 3b. When the fluid pressure in a space S3 in the inside circumference becomes higher than that in a space S4 in the outside circumference, the check-lip 105 comes apart by the differential pressure from the valve-seat face 3b; when the fluid pressure in the space S4 in the outside of the periphery of the space S3 on the inside of the periphery, the check-lip 105 is pressed by the differential pressure onto the valve-seat face 3b to shut off the fluid flow. In the above, specified numbers of recesses 105c are formed in positions appropriately apart from the tip of the lip in the faces opposite to the valve-seat face 3b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sealing device used as a shaft sealing means for a piston rod of a hydraulic shock absorber.

  A hydraulic shock absorber (shock absorber) of a vehicle is provided with a sealing device for sealing the circumference of the piston rod. FIG. 4 is a half sectional view showing a conventional sealing device cut along a plane passing through an axis O together with a part of a double cylinder type hydraulic shock absorber.

  The double cylinder type hydraulic shock absorber shown in FIG. 4 includes an outer cylinder 1 and an inner cylinder 2, a rod guide 3 that is attached across the ends of the outer cylinder 1 and the inner cylinder 2, and the rod guide 3. A piston rod 4 which is inserted in the inner periphery so as to be movable in the axial direction, and is attached to an inner end of a piston (not shown) which is inserted in the inner periphery of the inner cylinder 2 so as to be slidable in the axial direction; 3 is provided on the outer side in the axial direction of 3 and is fixed to the inner periphery of the open end of the outer cylinder 1 to seal the outer periphery of the piston rod 4.

  The sealing device 5 includes a flat washer-shaped metal ring 51 and a main lip 52, a dust lip 53, an outer peripheral lip 54, and a check lip 55 that are integrally formed with the metal ring 51 with rubber or rubber-like synthetic resin. Consists of.

  Of these, the main lip 52 extends from the inner peripheral portion of the metal ring 51 toward the inside of the hydraulic shock absorber, and a garter spring 56 is fitted on the outer periphery thereof so as to be slidably in contact with the outer peripheral surface of the piston rod 4. Thus, the hydraulic oil in the oil chamber S1 on the inner periphery of the inner cylinder 2 is prevented from leaking from the outer periphery of the piston rod 4 to the outside. The dust lip 53 extends from the inner peripheral portion of the metal ring 51 toward the opposite side (outer side) of the main lip 52, and is slidably in close contact with the outer peripheral surface of the piston rod 4, thereby causing dust from the outside. The outer peripheral lip 54 is provided on the outer peripheral portion of the metal ring 51 and is interposed between the outer peripheral portion of the rod guide 3 and the outer cylinder 1 in a compressed state. Thus, leakage of the hydraulic oil and gas from between the rod guide 3 and the outer cylinder 1 is prevented.

  The check lip 55 is provided on the outer peripheral side of the main lip 52 at the radial intermediate portion of the metal ring 51, extends in a tapered shape opened to the outer peripheral side, and has a tip formed on the rod guide 3. The seating surface 3b is in close contact with the seating surface 3b.

  In the process of moving the piston rod 4 in the axial direction in the direction of projecting to the outside, the volume of the oil chamber S1 is reduced by the movement of a piston (not shown) integrated with the piston rod 4, so that the hydraulic oil in the oil chamber S1 is reduced. A part flows through the gap G between the inner peripheral surface of the rod guide 3 and the outer peripheral surface of the piston rod 4 and flows into the main lip chamber S3 in which the main lip 52 is accommodated. For this reason, when the pressure of the hydraulic oil in the oil chamber S1 rises and becomes higher than the open chamber S4 on the outer peripheral side of the check lip 55, the check lip 55 opens due to the differential pressure and opens away from the valve seat surface 3b. The hydraulic oil in the main lip chamber S3 flows from the open chamber S4 to the reservoir chamber S2 through the communication hole 3d formed in the rod guide 3. Further, when the pressure introduced from the reservoir chamber S2 into the open chamber S4 through the communication hole 3d is higher than that of the main lip chamber S3, the check lip 55 is pressed against the valve seat surface 3b by the differential pressure. The valve functions as a check valve for preventing the gas in the reservoir chamber S2 from flowing back to the main lip chamber S3.

Therefore, in this type of sealing device 5, the check lip 55 maintains the sealing performance of the main lip 52 by keeping the pressure rise in the main lip chamber S3 below a certain level, and also provides a hydraulic buffer due to the inflow of gas into the oil chamber S1. This prevents a decrease in the damping performance of the vessel (see, for example, Patent Document 1 below).
Japanese Utility Model Publication No. 5-3739

  The sealing device 5 as described above maintains the sealing performance of the main lip 52 by suppressing the pressure rise in the main lip chamber S3 as much as possible, and reduces the frictional resistance of the main lip 52 against the outer peripheral surface of the piston rod 4 as much as possible. From the viewpoint of improving the pressure, it is necessary to reduce the valve opening pressure of the check lip 55 so that the rising pressure of the main lip chamber S3 can be quickly released. However, when the thickness of the check lip 55 is reduced to reduce the valve opening pressure or the crushing margin is reduced, the pressure in the reservoir chamber S2 (open chamber S4) is increased due to the reverse pressure. There is a concern that the check lip 55 is easily reversed to the inner peripheral side, and the function of preventing the gas in the reservoir chamber S2 from flowing back to the main lip chamber S3 is impaired.

  Further, when a rib is provided on the check lip for the purpose of preventing the reversal of the check lip as in Patent Document 1, the valve opening pressure is increased by increasing the rigidity of the check lip. It was difficult to maintain the sealing property and reduce the friction. Moreover, since the close width of the check lip is reduced by the rib, it is difficult to improve the check function when the pressure in the reservoir chamber increases.

  The present invention has been made in view of the above points, and a technical problem thereof is to open a check lip in a sealing device used as a shaft sealing means for a piston rod of a hydraulic shock absorber. The main purpose is to maintain the sealing performance of the main lip by reducing the pressure, to reduce the sliding resistance, and to prevent reversal of the check lip during reverse pressure.

  As means for effectively solving the above technical problem, a sealing device for a hydraulic shock absorber according to the present invention is provided on a main lip that is slidably in contact with an outer peripheral surface of a piston rod and an outer peripheral side thereof. The check lip extends in a tapered shape inclined toward the outer peripheral side and is opposed to the valve seat surface in the axial direction. The fluid pressure in the inner peripheral side of the check lip is higher than the outer peripheral side space. In this case, the fluid is allowed to flow away from the valve seat surface due to the differential pressure, and when the fluid pressure in the outer circumferential space is higher than the inner circumferential space, the differential pressure causes the fluid to flow. The fluid is pressed against the valve seat surface to block the flow of the fluid, and the required number of recesses are formed at a position appropriately separated from the lip tip of the surface facing away from the valve seat surface. It is. In this configuration, more preferably, the concave portion includes a plurality of grooves extending in parallel to each other in the circumferential direction of the check lip.

  According to the above configuration, the rigidity of the check lip is reduced by the recess formed on the surface facing the valve seat surface, that is, the valve opening pressure is reduced, so that the space on the inner peripheral side (main lip side) Even if the increase in the fluid pressure is relatively small, the check lip is deformed so as to separate from the valve seat surface and opens quickly. For this reason, the fluid pressure acting on the main lip is kept low, maintaining the sealing performance and reducing the sliding resistance with the piston rod.

  Conversely, when the fluid pressure in the outer space is higher than that in the inner space, the check lip is pressed against the valve seat surface by the differential pressure. And since the recessed part of a check lip is formed in the position suitably separated from the lip front-end | tip part, the deformation | transformation of the check lip by the said differential pressure becomes large in the position suitably distant from the front-end | tip part. For this reason, the close contact width of the check lip with respect to the valve seat surface is increased to provide an excellent check valve function, and the inversion to the inner peripheral side is less likely to occur.

  According to the sealing device for a hydraulic shock absorber according to the present invention, the main lip can be maintained and the sliding resistance can be reduced by reducing the valve opening pressure of the check lip, and the check lip can be prevented from being reversed and sealed when the reverse pressure is applied. Both improvements can be achieved.

  Hereinafter, preferred embodiments of a sealing device for a hydraulic shock absorber according to the present invention will be described with reference to the drawings. FIG. 1 is a half sectional view showing a sealing device for a hydraulic shock absorber according to the present invention by cutting along a plane passing through an axis O together with a part of a double cylinder type hydraulic shock absorber, and FIG. 2 is for explaining the operation thereof. FIG. 3 is a fragmentary cross-sectional view showing a modification of the cross-sectional shape of the groove.

  First, a double cylinder type hydraulic shock absorber shown in FIG. 1 includes an outer cylinder 1 and an inner cylinder 2, and a rod that is inserted into the inner periphery of the outer cylinder 1 in the vicinity of the opening end and attached to the opening end of the inner cylinder 2. The guide 3 is inserted into the inner periphery of the inner cylinder 2 through the inner periphery of the rod guide 3 so as to be movable in the axial direction, and is inserted into the inner end of the inner cylinder 2 so as to be slidable in the axial direction. A piston rod 4 to which a piston (not shown) is attached, and a sealing device 100 which is disposed on the axially outer side of the rod guide 3 and is fixed to the opening end of the outer cylinder 1 to seal the outer periphery of the piston rod 4. The inner circumference of the inner cylinder 2 is an oil chamber S1 filled with hydraulic oil, and a space between the outer cylinder 1 and the inner cylinder 2 is a reservoir chamber S2 filled with gas.

  The rod guide 3 is provided with a bearing sleeve 31 made of a synthetic resin material having a low friction coefficient, such as PTFE, which is excellent in wear resistance, on the inner peripheral surface, and is disposed on the outer side in the axial direction (the side opposite to the oil chamber S1 and the reservoir chamber S2). At the facing end, the innermost annular recess 3a, the valve seat surface 3b that protrudes axially outward from the outer periphery and forms a plane substantially perpendicular to the axis O, and the outermost recess An annular convex portion 3c protruding outward in the axial direction is formed.

  The sealing device 100 includes a flat washer-shaped metal ring 101 sandwiched and fixed by a caulking portion 1 a obtained by bending the opening end portion of the outer cylinder 1 to the inner periphery and an annular convex portion 3 c of the rod guide 3, and the metal ring 101. The main lip 102, the dust lip 103, the outer peripheral lip 104 and the check lip 105 are integrally formed of rubber or a synthetic resin having rubber-like elasticity.

  The main lip 102 in the sealing device 100 extends from the inner peripheral portion of the metal ring 101 toward the inside of the hydraulic shock absorber, and a garter spring 106 is fitted on the outer periphery, and the main lip formed by the annular recess 3 a of the rod guide 3. The hydraulic oil in the oil chamber S1 is prevented from leaking from the outer periphery of the piston rod 4 to the outside by being slidably in contact with the outer peripheral surface of the piston rod 4 while entering the chamber S3. is there. The main lip chamber S3 corresponds to the inner circumferential space described in claim 1.

  The dust lip 103 in the sealing device 100 extends from the inner peripheral portion of the metal ring 101 toward the opposite side (outer side) of the main lip 102, and is slidably brought into close contact with the outer peripheral surface of the piston rod 4. The outer peripheral lip 104 is in close contact with the inner peripheral surface of the outer tube 1 and the outer peripheral surface of the annular convex portion 3c of the rod guide 3 in an appropriate compressed state. The hydraulic oil and gas are prevented from leaking to the outside from between the rod guide 3 and the outer cylinder 1.

  The check lip 105 in the sealing device 100 is provided on the outer peripheral side of the main lip 102 at the radial intermediate portion of the metal ring 101, and as shown in FIG. In the mounted state, as shown in FIG. 2B, the valve seat surface 3b of the rod guide 3 is opposed in the axial direction and is in close contact with the valve seat surface 3b. An open chamber S4 is defined between the check lip 105 and the annular convex portion 3c of the rod guide 3, and the open chamber S4 is a reservoir chamber via a communication hole 3d formed in the outer peripheral portion of the rod guide 3. S2 communicates with each other. Note that the open chamber S4 corresponds to the outer peripheral space described in claim 1.

  On the surface of the check lip 105 facing the opposite side of the valve seat surface 3b of the rod guide 3, in other words, on the surface 105b on the open chamber S4 side, as a concave portion at a position appropriately separated from the tip portion 105a of the check lip 105, A plurality of grooves 105c extending in parallel to each other in the circumferential direction are formed. In the example shown in FIG. 2, the cross-sectional shape of the groove 105c is rectangular.

  Next, the operation of the hydraulic shock absorber shown in FIG. 1 will be described. Part of the hydraulic oil in the oil chamber S 1 is between the inner peripheral surface of the bearing sleeve 31 of the rod guide 3 and the outer peripheral surface of the piston rod 4. Is introduced into the main lip chamber S3 through the gap G, thereby lubricating the sliding portion between the bearing sleeve 31 and the piston rod 4 and the sliding portion between the main lip 102 and the piston rod 4 of the sealing device 100. ing.

  Further, when an axial relative motion between the outer cylinder 1 and the piston rod 4 is input due to an impact during travel of the vehicle, a piston (not shown) attached to the inner end of the piston rod 4 moves relative to the inner cylinder 2 in the axial direction. It moves, and a hydraulic damping force is generated when hydraulic oil flows between the oil chambers on both sides of the oil chamber through a restriction flow path provided in the piston. Therefore, the impact is effectively relieved and the vibration caused thereby is quickly converged.

  Here, in the process in which the piston rod 4 moves in the axial direction in the direction of projecting to the outside due to the impact input as described above, the volume of the oil chamber S1 decreases due to the movement of a piston (not shown) integral therewith, Part of the hydraulic oil in the oil chamber S1 flows into the main lip chamber S3 through a gap G between the inner peripheral surface of the bearing sleeve 31 of the rod guide 3 and the outer peripheral surface of the piston rod 4. For this reason, when the pressure of the hydraulic oil in the oil chamber S1 rises and becomes higher than the open chamber S4 on the outer peripheral side of the check lip 105, the differential pressure causes the check lip 105 to be separated from the valve seat surface 3b of the rod guide 3. Acts in the direction. The rigidity of the check lip 105 is reduced by a plurality of grooves 105c formed on the surface 105b on the open chamber S4 side and extending in parallel with each other in the circumferential direction, that is, the valve opening pressure is low. As shown by the broken line in FIG. 2 (B), the check lip 105 is deformed so as to be separated from the valve seat surface 3b by the pressure, and the hydraulic oil in the main lip chamber S3 is opened. Quickly flows into the reservoir chamber S2 through the communication hole 3d of the rod guide 3.

  Therefore, since the pressure in the main lip chamber S3 is kept relatively low, it is possible to effectively prevent the hydraulic oil from leaking from the main lip chamber S3 to the outside through the sliding portion of the main lip 102 and the piston rod 4. In addition, since the pressure in the main lip chamber S3 that acts as a pressing force of the main lip 102 against the piston rod 4 is kept low, sliding resistance and wear of the main lip 102 are also reduced.

  Further, in the process of moving the piston rod 4 in the axial direction in the direction in which the piston rod 4 is inserted into the inner cylinder 2, the movement of the piston (not shown) integral with the piston rod 4 causes the check lip 105 to move from the reservoir chamber S 2 through the communication hole 3 d. Since the pressure introduced into the outer open chamber S4 rises and becomes a reverse pressure state higher than that of the main lip chamber S3, the differential pressure causes the check lip 105 to be pressed against the valve seat surface 3b, and the inside of the reservoir chamber S2 It has a check valve function that prevents the gas from flowing back to the main lip chamber S3.

  The rigidity of the check lip 105 is smaller in the region where the plurality of grooves 105c are formed than in the front end portion 105a, and the pressure in the open chamber S4 also enters each groove 105c to the valve seat surface 3b. 2B, when the pressure in the open chamber S4 (differential pressure with respect to the main lip chamber S3) increases, the deformation of the check lip 105 causes the tip 105a to be deformed, as indicated by the alternate long and short dash line in FIG. It becomes larger at a position more appropriately separated. For this reason, the close contact width of the check lip 105 with respect to the valve seat surface 3b is increased to provide an excellent check valve function, and stress on the distal end portion 105a is relieved, and the inner periphery is reversed to the main lip chamber S3 side. Is less likely to occur.

  Further, since the groove 105c is formed on the surface 105b on the open chamber S4 side, the groove 105c is not cracked by receiving the bending deformation shown in FIG.

  In addition to the rectangular shape shown in FIG. 2, the groove 105c may have various shapes such as a V shape, a U shape, or a single belt shape as shown in FIG. There is no particular limitation.

1 is a half sectional view showing an embodiment of a sealing device for a hydraulic shock absorber according to the present invention by cutting along a plane passing through an axis together with a part of a double-cylinder hydraulic shock absorber. It is principal part sectional drawing for demonstrating the effect | action by this invention. It is principal part sectional drawing which shows the example of a change of the cross-sectional shape of a groove | channel. FIG. 10 is a half sectional view showing a conventional hydraulic shock absorber sealing device cut along a plane passing through an axis together with a part of a double cylinder type hydraulic shock absorber.

Explanation of symbols

3 Rod guide 3b Valve seat surface 4 Piston rod 100 Sealing device 101 Metal ring 102 Main lip 103 Dustrip 104 Outer lip 105 Check lip 105a Tip 105b Surface on the open chamber S4 side (surface facing the valve seat surface)
105c groove (concave)
S1 Oil chamber S2 Reservoir chamber S3 Main lip chamber (inner space)
S4 Open room (outer space)

Claims (2)

  A main lip that is slidably in close contact with the outer peripheral surface of the piston rod, and a check lip that is provided on the outer peripheral side and extends in a tapered shape inclined toward the outer peripheral side, and is opposed to the valve seat surface in the axial direction; The check lip allows the fluid to flow away from the valve seat surface due to the differential pressure when the fluid pressure in the inner circumferential space is higher than the outer circumferential space, and allows the fluid to flow. When the fluid pressure in the space on the outer peripheral side of the space becomes high, the fluid pressure is pressed against the valve seat surface by the differential pressure, and the flow of the fluid is blocked. A sealing device for a hydraulic shock absorber, wherein a required number of recesses are formed in positions facing away from the tip of the lip.   2. The sealing device for a hydraulic shock absorber according to claim 1, wherein the recess comprises a plurality of grooves extending in parallel with each other in the circumferential direction of the check lip.

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